Narrative:

Aircraft #1 at FL330 en route to bwi. Aircraft #2 FL310 en route atl. I was waiting for aircraft #1 to pass aircraft #2, so I could descend aircraft #1 to FL290. Aircraft were on opposite courses. After coordination with another sector on another matter, I went back and gave aircraft #1 descent clearance. Conflict alert was activated after aircraft #1 left FL330 on back side of aircraft #2.

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Original NASA ASRS Text

Title: ZDC CTLR MISJUDGES REQUIRED SEPARATION AND DSNDS A B733 CONFLICTING WITH A B752.

Narrative: ACFT #1 AT FL330 ENRTE TO BWI. ACFT #2 FL310 ENRTE ATL. I WAS WAITING FOR ACFT #1 TO PASS ACFT #2, SO I COULD DSND ACFT #1 TO FL290. ACFT WERE ON OPPOSITE COURSES. AFTER COORD WITH ANOTHER SECTOR ON ANOTHER MATTER, I WENT BACK AND GAVE ACFT #1 DSCNT CLRNC. CONFLICT ALERT WAS ACTIVATED AFTER ACFT #1 LEFT FL330 ON BACK SIDE OF ACFT #2.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.